Percutaneous transluminal angioplasty ("PTA") and percutaneous transluminal coronary angioplasty ("PTCA"), wherein a dilatation balloon is advanced through the vascular system to a stenosis and inflated to open the blockage, is now a commonplace procedure. In about one-third of the cases, however, the procedure leads to restenosis that can require another dilatation procedure. It is estimated that the total cost of restenosis requiring an additional dilatation procedure or some other treatment, is over 2 billion dollars per year worldwide.
Various agents that may reduce restenosis can be applied to the dilatation site. For example, antithrombolytic agents such as heparin may prevent clotting. Antiproliferative agents, such as dexamethasone, can prevent smooth muscle cell migration and proliferation.
Various methods have been proposed to effectively deliver such agents to the dilatation site. For example, in U.S. Pat. No. 5,087,244, to Wolinsky, a catheter is disclosed having a thin walled flexible balloon with a plurality of small holes. After an angioplastic procedure, such a balloon can be advanced to the dilatation site and inflated with heparin, or some other medication. The medication exits the inflated balloon, which is in contact with the arterial wall, through the holes.
U.S. Pat. Nos. 4,824,436 and 4,636,195, also to Wolinsky, disclose a catheter with a drug delivery conduit provided between a pair of occlusion balloons. An embodiment is disclosed wherein a dilatation balloon is also provided between the occlusion balloons enabling both dilatation and drug delivery with the same catheter.
Another dilatation-drug delivery catheter is disclosed in U.S. Pat. No. 4,994,033 to Shockey et al. There, a double layered balloon with small holes in its outer layer is provided. Medication is introduced between the two layers and inflation fluid is introduced into the interior portion of the balloon. The pressure of the inflation fluid dilatates the stenosis and forces the medication directly into the tissue being dilatated.
Drug delivery and dilatation-drug delivery catheters are typically advanced to the dilatation site along a guide wire, which is received within a guide wire lumen that extends through the entire shaft of the catheter. Due to frictional forces between the guide wire and the catheter, advancing and removing the catheter can be difficult and time consuming.
In addition, because the entire catheter covers the guide wire, in order to insert or replace an over-the-wire catheter, it is necessary that the guide wire protrude from the patient's body by a length greater than the length of the catheter. Such a guide wire would be about 300 cm. long, and the portion extending from the body would be about 230 cm. Otherwise, the guide wire cannot be secured and its position proximate a lesion cannot be maintained. Instead of such a long guide wire, an exchange wire can be connected to the portion of the guide wire extending from the body when exchanging catheters. Exchange wires need to be at least 180 cm. long. In either case, additional personnel are needed during the procedure to handle the long wire. Even with the additional personnel, manipulation of the catheters during an exchange can be awkward. The length and expense of the procedure are, therefore, unnecessarily increased.